In electric motors with position-dependent motor torque, a lowering of the summed torque is provided exactly in the overlap region of the phases which, from a certain torque level on, may no longer be compensated for by increasing the phase current, if the electric motor is configured as a switched reluctance motor. In other motor topologies, the motor torque-position characteristic shows alternating minima and maxima, the maxima occurring at the positions at which only one phase of the electric motor is energized, respectively.
The minima lie in the overlap regions between two successively energized phases. In this context, both phases are energized, but generate motor torques whose sum is smaller than the maximum motor torque generated by one phase.
When the position of the motor rotor is slowly and continuously changed, then the stopping position may coincide with a minimum of the motor torque-position characteristic in the adjusted end position. In the case of high load torque and large static friction, the electric motor may no longer reliably start from this position of a minimum.
Moreover, in the case of a large setpoint torque and a slow change of the torque during the actuating operation, there is a risk for the electric motor to stop while passing through a minimum of the summed torque due to the load torque and the friction.